Degradable filter for smoking articles

ABSTRACT

A filter ( 14 ) for a smoking article ( 10 ) comprises a segment of filtration material ( 16 ), the filtration material ( 16 ) comprising randomly oriented regenerated cellulose fibres and cellulose acetate fibers. The filtration material ( 16 ) further comprises triacetin. The filter ( 14 ) also includes a wrapper ( 18 ) circumscribing the segment of filtration material ( 16 ).

The present invention relates to a filter for a smoking article, thefilter comprising a segment of filtration material comprisingregenerated cellulose fibres, cellulose acetate fibers, and triacetin.The present invention also relates to a filter for a smoking article,the filter comprising a segment of filtration material comprisingregenerated cellulose fibers and a low molecular weight polyether. Thepresent invention also extends to smoking articles comprising suchfilters.

Filter cigarettes typically comprise a cylindrical rod of tobacco cutfiller surrounded by a paper wrapper and a cylindrical filter axiallyaligned in an abutting end-to-end relationship with the wrapped tobaccorod. The cylindrical filter typically comprises a filtration material,usually cellulose acetate tow, circumscribed by a paper plug wrap.Conventionally, the wrapped tobacco rod and the filter are joined by aband of tipping wrapper, normally formed of an opaque paper material,which circumscribes the entire length of the filter and an adjacentportion of the wrapped tobacco rod.

A number of smoking articles in which tobacco is heated rather thancombusted have also been proposed in the art. In heated smokingarticles, an aerosol is generated by heating a flavour generatingsubstrate, such as tobacco. Known heated smoking articles include, forexample, electrically heated smoking articles and smoking articles inwhich an aerosol is generated by the transfer of heat from a combustiblefuel element or heat source to a physically separate aerosol formingmaterial. During smoking, volatile compounds are released from theaerosol forming substrate by heat transfer from the fuel element andentrained in air drawn through the smoking article. As the releasedcompounds cool they condense to form an aerosol that is inhaled by theconsumer. Smoking articles in which a nicotine-containing aerosol isgenerated from a tobacco material, tobacco extract or other nicotinesource, without combustion or heating, are also known.

After a smoking article has been smoked and the remainder of the articlehas been discarded, it is desirable that the filter section degrade asquickly as possible. It would be desirable to provide a filter for asmoking article which facilitates this.

According to a first aspect of the present invention, there is provideda filter for a smoking article, the filter comprising a segment offiltration material, wherein the filtration material comprises randomlyoriented regenerated cellulose fibres and cellulose acetate fibers. Thefiltration material further comprises triacetin, and the filter alsoincludes a wrapper circumscribing the segment of filtration material.

The term “regenerated cellulose fibres” is used herein to mean cellulosefibres which have been formed by processing a naturally occurringcellulose material to provide cellulose fibres having a desiredphysically property. A typical process for forming regenerated cellulosefibres includes the steps of: pulping a naturally occurring cellulosematerial, such as wood chips, to form a pulp; subjecting the pulp to oneor more treatment steps to alter the physical properties of thecellulose; and forming fibers of regenerated cellulose from the treatedpulp, for example by spinning cellulose fibres by passing the pulpthrough a spinneret.

Advantageously, using a filtration material that comprises randomlyoriented regenerated cellulose improves the degradation of thefiltration material. This is because the randomly oriented fibres canmore easily disperse after the filter has been discarded, particularlywhen compared with the substantially continuous filaments of traditionalcellulose acetate tow filters. Increased dispersion of the fibresincreases the exposure of the individual fibres to the environment, thusincreasing the rate at which the filtration material degrades.

Furthermore, despite using regenerated cellulose fibers in thefiltration material, filters in accordance with the present inventiondeliver a similar taste to the consumer when compared with traditionalcellulose acetate tow filters. The similar taste sensation is due to thecellulose acetate fibers and the triacetin binder present in thefiltration material of filters in accordance with the present invention.Moreover, whilst the triacetin binds to the cellulose acetate fibers toimprove the structural integrity of the filtration material, thetriacetin does not bind to the regenerated cellulose fibers, thusmaintaining the improved degradation of the filtration material.

The inventors have also recognised that filters consisting of onlyregenerated cellulose fibers do not exhibit the same levels of selectivephenol retention during smoking of the smoking article when compared totraditional cellulose acetate filters. Therefore, filters in accordancewith the present invention address this problem by incorporatingcellulose acetate fibers and triacetin into the filter with theregenerated cellulose fibers.

The triacetin is preferably present in an amount of about 1% to about15% by weight of the filtration material in the filter segment, morepreferably about 5% to about 10% by weight of the filtration material inthe filter segment, most preferably about 3% to about 5% by weight ofthe filtration material in the filter segment. In some embodiments, thefiltration material further comprises a low molecular weight polyetherto further increase the ability of the filter to selectively retainphenols during smoking of the smoking article. A suitable polyether ispolyethylene glycol. Preferably, the polyethylene glycol has a numberaverage molecular weight of between about 200 and about 3600, preferablybetween about 400 and about 1600.

The use of a low molecular weight polyether to increase the selectivephenol retention of a filtration material comprising randomly orientedregenerated cellulose fibers is itself a novel and inventivearrangement. Therefore, according to a second aspect of the presentinvention, there is provided a filter for a smoking article, the filtercomprising a segment of filtration material, the filtration materialcomprising randomly oriented regenerated cellulose fibres and a lowmolecular weight polyether. The filter further comprises a wrappercircumscribing the segment of filtration material.

As discussed above, incorporating a low molecular weight polyether intothe filtration material improves the selective phenol retention of thefiltration material. This may be important where a regenerated cellulosefilter is used to replace a traditional cellulose acetate tow filter,for example, since regenerated cellulose fibers exhibit less selectivephenol retention when compared to traditional cellulose acetate. The useof a low molecular polyether to improve the selective phenol retentionof a regenerated cellulose filter is illustrated in the examples shownin Table 1 below:

TABLE 1 catechol phenol m + p cresols μg/mg μg/mg μg/mg nicotinenicotine nicotine Cellulose acetate with 7% triacetin 56.548 10.158 8.439 100% Lyocell 69.798 38.973 20.191 100 parts Lyocell + 5 partsPEG400 56.159 23.155 13.932 Comparison of retention of different phenolsby a traditional cellulose acetate filter, a regenerated cellulose(Lyocell) filter, and a regenerated cellulose (Lyocell) + polyethyleneglycol (PEG) filter. The data represents the amount of each phenol whichpasses through the filter (that is, the amount of phenol not retained bythe filter) when the article is smoked. The data is normalised withrespect to the amount of nicotine which is also passes through thefilter during smoking of the article. The data was collected using asmoking test in accordance with ISO 4387: Determination of total andnicotine-free dry particulate matter using a routine analytical smokingmachine.

A suitable polyether is polyethylene glycol. Preferably, thepolyethylene glycol has a number average molecular weight of betweenabout 200 and about 3600, preferably between about 400 and about 1600.

To further improve the function of the filter to selectively removephenols during the smoking of the smoking article, the filtrationmaterial may include triacetin. Including triacetin also helps toincrease filter stiffness, which reduces the likelihood of filtercollapse during handling of the smoking article and during smoking. Inembodiments comprising triacetin, the triacetin is preferably present inan amount of about 1% to about 15% by weight of the filtration materialin the filter segment, more preferably about 5% to about 10% by weightof the filtration material in the filter segment, most preferably about3% to about 5% by weight of the filtration material in the filtersegment.

Preferably, filtration materials in accordance with both aspects of thepresent invention will degrade by at least about 30%, more preferably atleast about 40%, more preferably at least about 50%, within less thanabout 40 days, preferably less than about 30 days, when measured inaccordance with either of the following tests:

ISO 14855-2005, TEST1: aerobic biodegradation under controlledcomposting conditions

ISO 14851-2004, TEST2: aquatic aerobic respirometric biodegradation test

To illustrate the improved degradation of a filter including regeneratecellulose fibers when compared to a traditional cellulose acetatefilter, a comparison of the degradation of different filters under ISO14851-2004, TEST2 is shown in Graph 1 below:

The random orientation of the fibres in filters according to the presentinvention advantageously provides the required resistance of thefiltration material to mechanical deformation, such that the filter canwithstand being grasped by the consumer during smoking of the smokingarticle. The random orientation of the fibres also provides the requiredresistance to draw such that the smoking experience using filters inaccordance with the present invention is substantially the same as thesmoking experience using a traditional cellulose acetate tow filter.Filters in accordance with both aspects of the present invention mayhave a resistance to draw of between about 40 mm WG and about 250 mm WGfor a filter length of 27 millimetres, preferably from about 75 mm WG toabout 175 mm WG for a filter length of 27 millimetres, and mostpreferably from about 100 mm WG to about 150 mm WG for a filter lengthof 27 millimetres. Resistance to draw is measured using the testprocedure described in ISO 6565:2002.

Preferably, the regenerated cellulose fibres are crimped staple fibres,which helps to reduce mechanical degradation of the fibres duringprocessing of the filtration material to form the filter, and duringsubsequent assembly of the smoking article. The fibres can be crimpedusing a known method for crimping textile fibres, such as the methoddescribed in U.S. Pat. No. 2,647,285.

The crimped staple fibres preferably have a stretched length of betweenabout 10 mm and about 30 mm under a tension of between about 5 cN/denierand about 10 cN/denier. This provides an optimum balance between themechanical integrity of the filter during use and the rate of dispersionof the filtration material after the filter has been discarded. The term“stretched length” is used herein to mean the average length of thecrimped regenerated cellulose staple fibres when stretched under a giventensional load.

Preferably the crimped staple fibres have a denier of between about 0.5and about 8.0, preferably between about 1.5 and about 5.5, mostpreferably between about 2.0 and about 3.2.

Preferably the staple fibres have a crimped rate of between about 3curves and about 10 curves per 10 mm of fibre length, more preferablybetween about 6 curves and about 8 curves per 10 mm of fibre length.

The regenerated cellulose fibres may comprise Lyocell fibres. Lyocellfibres are defined as a regenerated cellulose fibre that is obtained byan organic solvent spinning process. Lyocell fibres suitable for use infilters according to the present invention are commercially availablefrom Lenzing Aktiengesellschaft under the trademark Tencel®.Advantageously, the process of manufacturing Lyocell fibres is moreenvironmentally friendly when compared with the manufacture oftraditional cellulose acetate, as well as other regenerated cellulosematerials such as rayon, viscose, and such like.

In particular, the manufacture of cellulose acetate uses catalyticagents containing cobalt or manganese. The manufacture of celluloseacetate also produces a strong, unpleasant odour. In contrast, thecellulose or ground pulp used to form Lyocell is treated in aclosed-loop process in which non-toxic solvents are recycled with arecovery rate of up to 99.5%. Furthermore, bleaching agents are notrequired in the production of Lyocell fibres. Any remaining emissionsfrom the manufacture of Lyocell can be decomposed in biologicalpurification plants.

The filtration material may include other fibres in addition to theregenerated cellulose fibres. Such additional fibres can be incorporatedinto the filter by mixing the additional fibres with the regeneratedcellulose fibres during manufacture of the filtration material. Theadditional fibres may be bound to the regenerated cellulose fibres usinga suitable water-soluble binder, such as those discussed above. Forexample, the filtration material of filters in accordance with thesecond aspect of the present invention may include cellulose acetatefibres to increase the mechanical strength of the filter. Alternatively,or in addition, the filtration material may include additional fibreswhich alter the appearance of the filtration material. For example, theappearance of the filtration material of filters in accordance with bothaspects of the present invention may be altered to more closely resemblethe appearance of a traditional cellulose acetate tow filter. Exemplaryfibres for altering the appearance of the filtration material includesilk, cotton, polyester, linen, nylon and wool.

To further improve the rate of dispersion and degradation of the filterafter it has been discarded, the wrapper may comprise a dissolvable plugwrap. The term “dissolvable” is used herein to mean that the plug wrapis capable of dissolving into a solution with water.

Advantageously, a dissolvable plug wrap will break open and disperseupon contact with water after the filter has been discarded, thereforeexposing the underlying filtration material to the environment andincreasing the rate of dispersion and degradation of the filtrationmaterial. In addition to being dissolvable, the plug wrap may bebiodegradable.

In embodiments including a dissolvable plug wrap, the plug wrapcomprises or consists of a sheet of polymeric film, wherein thepolymeric film includes at least one water-soluble polymer. Using apolymeric film to form the plug wrap reduces cost and simplifies themanufacture of the plug wrap. Specifically, in contrast to a papermaterial, a polymeric film can be formed to inherently posses therequired properties of a plug wrap, such as low gas permeability,without the need for any further processing steps during manufacture.

Furthermore, where it is desirable for the plug wrap to be transparent,it is easier to provide a transparent polymeric film than a transparentpaper.

Preferably, a 5 mm by 5 mm square sample of the polymeric film willdissolve in less than 72 hours when placed in 25 ml of distilled waterat a temperature of 22° C. The test is carried out in a container sizedsuch that the depth of water is sufficient to completely submerge thesquare sample (although the buoyancy of the sample may be such that itfloats on the surface of the water during the test). The sample isdeemed to have dissolved when the water-soluble material is no longervisible to the naked eye.

Suitable polymeric materials for forming the polymeric film include, butare not limited to, polyvinyl alcohol, cellophane, starch,hydroxypropylmethyl cellulose (HPMC), carboxymethyl cellulose andcombinations thereof.

Suitable polymeric films may be made entirely of one or morewater-soluble polymers or may include additional polymers or inertinorganic fillers, which may or may not be dissolvable. The polymericfilm may be single-layered or multi-layered. Where the film comprisesmultiple layers, the layers may be formed from the same polymericmaterials or they may be formed from different polymeric materials.Where the layers are formed from different polymeric materials, eachpolymeric material comprises at least one water-soluble polymer.

According to the present invention, there is also provided a smokingarticle comprising an aerosol-forming substrate and a mouthpiece securedin axial alignment with the aerosol-forming substrate, the mouthpiececomprising a filter according to either aspect of the present invention.

As used herein, the term ‘aerosol-forming substrate’ is used to describea substrate capable of releasing upon heating volatile compounds, whichcan form an aerosol. The aerosols generated from aerosol-formingsubstrates of smoking articles described herein may be visible orinvisible and may include vapours (for example, fine particles ofsubstances, which are in a gaseous state, that are ordinarily liquid orsolid at room temperature) as well as gases and liquid droplets ofcondensed vapours.

Smoking articles according to the present invention may be filtercigarettes or other smoking articles in which the aerosol-formingsubstrate comprises tobacco material or another combustible materialthat is combusted to form smoke. Alternatively, smoking articlesaccording to the present invention may be articles in which theaerosol-forming substrate comprises material that is heated to form anaerosol, rather than combusted. In one type of heated smoking article,tobacco material or another aerosol forming material is heated by one ormore electrical heating elements to produce an aerosol. In another typeof heated smoking article, an aerosol is produced by the transfer ofheat from a combustible or chemical heat source to a physically separateaerosol forming material, which may be located within, around ordownstream of the heat source. The present invention further encompassessmoking articles in which a nicotine-containing aerosol is generatedfrom a tobacco material, tobacco extract or other nicotine source,without combustion or heating.

Test Procedures ISO 14855-2005

The controlled composting biodegradation test is an optimised simulationof an intensive aerobic composting process where the biodegradability ofa test under dry aerobic conditions is determined. The inoculum consistsof stabilised and mature compost derived from the organic fraction ofmunicipal solid waste. The test item is mixed with the inoculum andintroduced into static reactor vessels where it is intensively compostedunder optimum oxygen, temperature and moisture conditions. The test isperformed according to ISO 14855 (2005) method “Determination of theUltimate Aerobic Biodegradability and Disintegration of Plastics underControlled Composting Conditions”, but in duplicate instead of intriplicate.

ISO 14851-2004

This test determines the aquatic, aerobic biodegradation underlaboratory conditions. The test material is placed in a chemicallydefined liquid medium and spiked with micro-organisms. During theaerobic degradation, oxygen is consumed and carbonaceous material isconverted to gaseous CO₂. NaOH pellets trap the CO₂ released and theinduced-pressure drop is directly related to the consumed oxygen and thebiodegradation of the test material.

The invention will now be further described, by way of example only,with reference to the accompanying drawings in which:

FIG. 1 shows a smoking article in accordance with an embodiment of thepresent invention; and

FIG. 2 shows the smoking article of FIG. 1 with the filter unwrapped.

The filter cigarette 10 shown in FIGS. 1 and 2 comprises a wrapped rod12 of tobacco cut filler which is attached at one end to an axiallyaligned filter 14 in accordance with the present invention. The filter14 comprises a single segment of filtration material 16, the filtrationmaterial 16 comprising randomly oriented regenerated cellulose fibresand cellulose acetate fibers, and triacetin. The filtration material 16may also include other fibres to alter the appearance of the filtrationmaterial 16, such as silk fibres. The filtration material 16 may alsocomprise one or more binders and may include one or more additives toimprove selective phenol retention. The segment of filtration material16 is circumscribed by a plug wrap 18, which may be dissolvable and mayconsist of a sheet of polymeric film comprising at least onewater-soluble polymer. The wrapped tobacco rod 12 and the filter 14 arejoined by a band 20 of tipping paper, which circumscribes the entirelength of the filter 14 and an adjacent portion of the wrapped tobaccorod 12. It will be appreciated that whilst the specific embodimentdescribed above relates to conventional smoking articles comprising afilter and a tobacco rod, a similar arrangement of a filter inaccordance with the present invention could also be used on a heatedsmoking article.

1. A filter for a smoking article, the filter comprising: a segment offiltration material, the filtration material comprising randomlyoriented regenerated cellulose fibres and cellulose acetate fibers, thefiltration material further comprising triacetin; and a wrappercircumscribing the segment of filtration material.
 2. The filter ofclaim 1, wherein the filtration material further comprises a lowmolecular weight polyether.
 3. The filter of claim 1, wherein thefiltration material comprises additional fibres selected from the groupconsisting of silk, cotton, polyester, linen, nylon, wool andcombinations thereof
 4. The filter of claim 1, wherein the triacetin ispresent in an amount of 1% to 15% by weight of the filtration material.5. A filter for a smoking article, the filter comprising: a segment offiltration material, the filtration material comprising randomlyoriented regenerated cellulose fibres and a low molecular weightpolyether; and a wrapper circumscribing the segment of filtrationmaterial.
 6. The filter of claim 2, wherein the low molecular weightpolyether comprises polyethylene glycol.
 7. The filter of claim 6,wherein the polyethylene glycol has a number average molecular weight ofbetween 200 and
 3600. 8. The filter of claim 1, wherein the regeneratedcellulose fibres are crimped staple fibres.
 9. The filter of claim 8,wherein the crimped staple fibres have a stretched length of between 10mm and 30 mm under a tension of between 5 cN/denier and 10 cN/denier.10. The filter of claim 8 or 9, wherein the crimped staple fibres have adenier of between 0.5 and 8.0 and a crimped rate of between 3 and 10curves per 10 mm fibre length.
 11. The filter of claim 1, wherein theregenerated cellulose fibres are Lyocell fibres.
 12. The filter of claim1, wherein the wrapper comprises a dissolvable plug wrap consisting of asheet of polymeric material, wherein the polymeric material comprises atleast one water-soluble polymer.
 13. A smoking article comprising: anaerosol-forming substrate; and a mouthpiece secured in axial alignmentwith the aerosol-forming substrate, the mouthpiece comprising a filteraccording to claim
 1. 14. A smoking article comprising: anaerosol-forming substrate; and a mouthpiece secured in axial alignmentwith the aerosol-forming substrate, the mouthpiece comprising a filteraccording to claim
 5. 15. The filter of claim 5, wherein the lowmolecular weight polyether comprises polyethylene glycol.
 16. The filterof claim 15, wherein the polyethylene glycol has a number averagemolecular weight of between 200 and
 3600. 17. The filter of claim 5,wherein the regenerated cellulose fibres are crimped staple fibres. 18.The filter of claim 17, wherein the crimped staple fibres have a denierof between 0.5 and 8.0 and a crimped rate of between 3 and 10 curves per10 mm fibre length.
 19. The filter of claim 5, wherein the regeneratedcellulose fibres are Lyocell fibres.
 20. The filter of claim 5, whereinthe wrapper comprises a dissolvable plug wrap consisting of a sheet ofpolymeric material, wherein the polymeric material comprises at leastone water-soluble polymer.